Inhibition of cytokine-primed eosinophil chemotaxis by nedocromil sodium

Background: Eosinophil influx into the lung tissue is considered to be relevant for the pathogenesis of asthma. Various chemotactic factors may be responsible for this influx. Recently it has been demonstrated that the cytokines granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), and interleukin-5 (IL-5) are present in the circulation of individuals with allergic asthma. These cytokines have the capacity to modulate chemotactic responses of eosinophils toward platelet-activating factor, formyl-methionyl-leucyl-phenylalanine, (FMLP) and neutrophil-activating factor (NAF)/IL-8, but not toward complement fragment C5a (C5a). Here the effect of nedocromil sodium on the chemotactic response of eosinophils from allergic asthmatic individuals and from normal donors preincubated with GM-CSF or IL-3 toward FMLP, NAF/IL-8 was evaluated. Results: Nedocromil sodium inhibited the chemotactic response toward FMLP and NAF/IL-8 of GM-CSF primed eosinophils approximately 60% (inhibitory concentration of 50% (IC₅₀]∼-1 to 10 nmol/L), whereas these responses of IL-3 primed eosinophils was completely inhibited (IC₅₀∼1 nmol/L). Conclusions: The chemotactic responses toward C5a were inhibited by nedocromil sodium at higher concentrations than were required in the priming studies (IC₅₀∼10 to 100 nmol/L). Nedocromil sodium (0.1 μmo/L) was also effective in inhibiting the chemotactic response toward FMLP (10 nmol/L) of eosinophils isolated from the circulation of patients with allergic asthma 3 hours after allergen challenge. These findings might explain in part the antiinfiammatory action of nedocromil sodium.